Opportunity to view the starry night sky is linked to human emotion and behavioral interest in astronomy

Prior to the modern era, the stars in the night sky were readily visible across the globe, but light pollution has created disparities in the opportunity to see these astronomical objects with the naked eye. This alteration may measurably impact human behavior. We hypothesize that light pollution is related to the development of people’s interest in astronomy, which often serves as a “gateway” to science more broadly. In a state-by-state analysis, we used location information to examine astronomy interest data for millions of US residents. Results show that, among populations with low light pollution, a feeling of “wonder about the universe” is prevalent (r = 0.50). We found that this human emotion mediates the association between low light pollution and behavioral interest in astronomy. Although the effects of light pollution on astronomy, biology, ecology, and health are well-known, the present work demonstrates that light pollution is also relevant to human scientific behavior, with broad implications for science education and society.


Light pollution and wonder about the universe
Our analyses of these two independent datasets show a positive association at the state level between low light pollution and feelings of wonder about the universe, r = 0.50, p < 0.001 (Fig. 1c).Importantly, the Pew survey also measured three other psychological questions that served as controls in the present study, because they were collected in randomized order on the same individuals who answered the question about wonder (specifically, Pew collected measures of gratitude/thankfulness, spiritual peace/well-being, and meaning/purpose of life, Supplementary Information, Sect.1.2).These psychological variables also varied by state across the US (Supplementary Fig. 1), but there was no significant association (ps > 0.27) between low light pollution and any of these control covariates (Fig. 1c).
For completeness, we note that for a sample of 50 (df = 48), a Pearson r coefficient would need to meet or exceed r = 0.28 [absolute value] to achieve p < 0.05.Also, because the low light pollution data were skewed, necessitating interpretive caution, we re-calculated the r using a dichotomous median split for the light pollution data, and found that the correlation remained significant, see Supplementary Information, Sect. 2.

Wonder about the universe and astronomy interest
Psychological perspectives hold that emotions such as wonder can drive learning and exploration 30,31 .We hypothesized that wonder about the universe would be associated with behavioral interest in astronomy, and developed eight measures of such interest at the state level (Supplementary Information, Sects.1.3-1.9).
The first measure was seeking to learn about astronomy.Using the billions of searches conducted on Google 32 , we found that states with more wonder about the universe also have a higher proportion of total internet searches for "astronomy, " r = 0.52, p < 0.001 (Supplementary Information, Sect.1.3 and Supplementary Fig. 2a).
Second, we examined people's interest in contributing to astronomical knowledge.We found a positive association between state-level wonder about the universe and the percent of the state population that submits data to the NSF-NOIRLab's citizen scientist project Globe at Night 33 , r = 0.40, p = 0.004 (Supplementary Information, Sect.1.4 and Supplementary Fig. 2b).Third, interest in astronomy may be seen more broadly in popular culture, and Nobel laureate astrophysicist Kip Thorne consulted on a scientifically-grounded film depiction of exoplanetary exploration, Interstellar 34 .State-level wonder was positively associated with the state-level proportion of peoples' web video searches for Interstellar, r = 0.50, p < 0.001 (Supplementary Information, Sect.1.5 and Supplementary Fig. 2c).
The fourth and fifth analyses were conducted on a measure of peoples' interest in voyaging to another planet.Specifically, signing up to have their name inscribed on a chip and sent to Mars affixed to NASA's InSight lander and Perseverance rover.State-level wonder about the universe was positively associated with the percent of the state population that submitted their name to voyage aboard InSight, r = 0.56, p < 0.001, and Perseverance, r = 0.65, p < 0.001 (Supplementary Information, Sect.1.6 and Supplementary Fig. 2d,e).
Sixth, people can take concrete steps to send their physical selves into space by training to become an astronaut.In 2020, NASA invited astronaut applications from those with documented STEM backgrounds, and more than 12,000 applied to join this "Artemis Generation."We submitted a Freedom of Information Act (FOIA) request to NASA, and they released to us the number of astronaut applications from each of the states.State-level wonder about the universe was positively associated with the percent of people from each state with STEMrelated backgrounds who applied to become a NASA astronaut, r = 0.34, p = 0.017 (Supplementary Information, Sect.1.7 and Supplementary Fig. 2f.).
Seventh, the James Webb Space Telescope (JWST) is NASA's latest large strategic science mission 27 , and millions of people "follow" the telescope via Twitter (now X).We found that state-level wonder about the universe was positively associated with the percent of the state population that follows @NASAWebb, r = 0.53, p < 0.001 (Supplementary Information, Sect.1.8 and Supplementary Fig. 2g).
Eighth, wonder about the universe may correlate with general interest in NASA, which can be indexed by subscriptions to the NASA Newsletter.Via a FOIA request, we received more than 975K de-identified records from NASA and found that state-level wonder about the universe was positively associated with the percent of the state population subscribed to NASA's Newsletter, r = 0.37, p = 0.009 (Supplementary Information, Sect.1.9 and Supplementary Fig. 2h).
Finally, we formed a composite measure of "behavioral interest in astronomy" (Fig. 1d; also see Supplementary Information, Sect.1.10).As expected, there was a significant positive association between this state-level composite measure of behavioral interest in astronomy and state-level feelings of wonder about the universe (from the Pew survey), r = 0.64, p < 0.001 (Fig. 2a).Also as expected, there were no significant associations between behavioral interest in astronomy and the other variables from the Pew survey that served as controls in this study (Fig. 2b-d).

Mediation analyses
We used statistical mediation models to assess the connections among light pollution, wonder about the universe, and behavioral interest in astronomy, using 95% confidence intervals with 5,000 bootstrap samples 35 .If a variable is demonstrated to serve as a "mediator, " it can be said to serve as a link between two other variables 35 (see Methods).We examined whether wonder about the universe mediates between light pollution and behavioral interest in astronomy, even when controlling for other possible demographic covariates.
In this mediation analysis, we tested whether the observed positive association between low light pollution and behavioral interest in astronomy, r = 0.45, p < 0.001, was mediated by wonder about the universe.As hypothesized, this effect was obtained: mediator effect ab = 0.21, 95% C.I. [0.09, 0.35] (Fig. 3a,b).Additionally, we examined potential confounders: education, poverty, race, population size, and population density (Supplementary Information, Sect.1.11).When including these covariates, wonder about the universe was still a significant mediator between light pollution and behavioral interest in astronomy, mediator effect ab = 0.14, 95% C.I. [0.04, 0.28], and education was the only covariate associated with behavioral interest in astronomy (see Table 1).When we performed sensitivity analyses by analyzing the data using alternative models, we obtained substantively similar results (Supplementary Information, Sect.3).

Discussion
Light pollution has adverse consequences for biological and ecological systems [4][5][6][7][8][9][10][11][12][13]36 as well as for the science of astronomy itself 1,2,37 . Hoever, its effects on human behavior have been understudied. In thi investigation, by combining data from the physical and psychological sciences, we showed that low light pollution is linked with the tendency of the population to feel wonder about the universe and to become interested in exploring it.This association exhibited some specificity-other psychological measures that had been measured in the same individuals at the same time in tandem with wonder about the universe were not associated with light pollution.The inclusion of multiple demographic covariates did not change the significant findings in the mediation model.That is, the mediation modelling still showed that a psychological factor (wonder about the universe) mediated the association between the physical environment (light pollution) and human behavior (interest in astronomy).
These findings suggest that humans' loss of the opportunity to see the starry night sky is related to peoples' behavior.From a human developmental and educational perspective, one is immediately drawn to the question of whether light pollution may influence the development of children's and adolescents' interest in science [38][39][40][41] .For example, seeing the starry night sky might prompt youths to think more about the physical universe, and to join relevant social/academic affinity groups to advance this knowledge as they develop academically 42,43 .One empirical study in central coastal California (a region of somewhat low light pollution) found that children as young as three-and four-years of age express curiosity about astronomical objects, asking caregivers for explanations (e.g., "Why do the stars shine?") 44 .The opportunity to see the stars in the night sky could engender interest in astronomy and greater chances of gaining practice in everyday scientific thinking.Indeed, many astronomers report that, in their youth, seeing the night sky triggered a feeling of "wonder" about the universe, and that this  www.nature.com/scientificreports/ was a motivator for them aspiring to become a scientist [20][21][22][23][24]45 . Furher psychological work is needed to understand how children's feelings of wonder and awe [46][47][48] interact with early caregiver support 44,49 and experiences in formal education 50,51 to promote interest and engagement with astronomy, the natural world, and the process of science to address questions about the universe.Additionally, data from diverse cultures are needed.This is especially the case for Africa, Latin America, Oceania, as well as European countries where light pollution is rapidly encroaching upon formerly pristine dark skies 52,53 .To combat this, light pollution researchers 54 and architects 55 are proposing interventions on lighting practices.Keeping light pollution in check may nurture "citizen science" 1,2,33 which, itself, engenders public enthusiasm and financial support for science 27 . When interdsciplinary teams of scientists partner with communities most affected by light pollution (and other environmental challenges 56,57 ) both science and society can benefit [58][59][60][61][62] .
We acknowledge two limitations of the present work.First, our findings are at the level of the US states and do not apply to individual people, which logically constrains the inferences that can be drawn 63,64 .Research that examines light pollution, wonder about the universe, and astronomy interest within the same individual, rather than at the state level, is needed.A second limitation is that correlations do not specify causality, and it remains possible that those who have an interest in astronomy, or a sense of wonder about the universe, may choose to live in low light pollution states.To more directly address causality, longitudinal studies of people as they develop intellectual interests, coupled with random-assignment educational interventions, would be valuable.

Conclusion
Light pollution is recognized as an international concern.UNESCO representatives, government officials, and scientists jointly authored the La Palma Declaration, classifying the unpolluted night sky as an "inalienable right of humankind" 65 .Astronomers 1 and light pollution researchers 66 are calling for concrete actions to curb light pollution.As suggested here, increasing access to the starry night sky may also help to promote more equitable opportunities to feel wonder about the universe, which can motivate interest and engagement in science 20,67 .The present findings thus begin to suggest how light pollution is not only impacting biological and ecological processes, but also human behavior, science education, and society.

Analytic strategy
All analyses used the 50 US states 68 .All measures were z-scored to allow construction of the composite score, and to facilitate comparisons among the measures and between the states.Positive/negative z-scores indicate the values are above/below the central tendency of the distribution for that measure.Prior to mediation analyses, regression assumptions were checked and met.

Mediation analysis method
In mediation analysis 35 , the predictor variable X is examined for its effect on mediator variable M (Path a), and M is examined for its effect on outcome variable Y (Path b).The mediator (indirect) effect, ab, is the product of Path a and Path b.The effect of X on Y is Path c. Path c' is the effect of X on Y while accounting for M. Mediation was tested with Hayes' PROCESS modeling tool (Model 4) 35 .

Figure 1 .
Figure 1.State maps of low light pollution, wonder about the universe, astronomy interest, and correlations between measures.(a) Map of US states showing low light pollution 28 , purple (darker purple indicates less light pollution).(b) Map of US states showing respondents' sense of wonder about the universe from the Pew Research Center 29 , pink (darker pink indicates more wonder about the universe).(c) Pearson correlations between low light pollution and wonder about the universe, and between low light pollution and other psychological emotions.(d) Map of US states showing composite measure of behavioral interest in astronomy, blue (darker blue indicates more interest in astronomy).All measures are z-standardized and defined in the Supplemental Information (also see Methods).

Figure 2 .
Figure 2. Scatterplots of association of wonder about the universe (and other emotions) with behavioral interest in astronomy (N = 50 states).(a) scatterplot showing significant correlation between wonder about the universe and composite measure of behavioral interest in astronomy (pink).(b-d) Scatterplots of the nonsignificant correlations between other control psychological measures and composite measure of behavioral interest in astronomy (gray).Shaded areas show 95% confidence intervals.All measures are z-standardized (see Methods).

Figure 3 .
Figure 3. Mediation analysis.(a) Beta weights of the regression coefficients in mediation model showing low light pollution correlated with wonder about the universe (Path a) and wonder about the universe correlated with interest in astronomy (Path b), with the mediator (indirect) effect ab = 0.21.***p < 0.001.(b) Smoothed density plots showing distribution of bootstrapped beta values produced in (a) by Hayes' PROCESS Model 4 35 with the following indicators: dashed vertical red line (beta value of zero), solid horizontal orange lines (95% confidence intervals of bootstrapped beta values), orange squares (medians of bootstrapped beta values).